This needs to make it in before 3.7 is released. -- There have been some 3.7-rc reports of vm issues, including some kswapd bugs and, more importantly, some memory "leaks": http://www.spinics.net/lists/linux-mm/msg46187.html https://bugzilla.kernel.org/show_bug.cgi?id=50181 The post-3.6 commit 1fb3f8ca took split_free_page() and reused it for the compaction code. It does something curious with capture_free_page() (previously known as split_free_page()): int capture_free_page(struct page *page, int alloc_order, ... __mod_zone_page_state(zone, NR_FREE_PAGES, -(1UL << order)); - /* Split into individual pages */ - set_page_refcounted(page); - split_page(page, order); + if (alloc_order != order) + expand(zone, page, alloc_order, order, + &zone->free_area[order], migratetype); Note that expand() puts the pages _back_ in the allocator, but it does not bump NR_FREE_PAGES. We "return" 'alloc_order' worth of pages, but we accounted for removing 'order' in the __mod_zone_page_state() call. For the old split_page()-style use (order==alloc_order) the bug will not trigger. But, when called from the compaction code where we occasionally get a larger page out of the buddy allocator than we need, we will run in to this. This patch simply changes the NR_FREE_PAGES manipulation to the correct 'alloc_order' instead of 'order'. I've been able to repeatedly trigger this in my testing environment. The amount "leaked" very closely tracks the imbalance I see in buddy pages vs. NR_FREE_PAGES. I have confirmed that this patch fixes the imbalance Signed-off-by: Dave Hansen <dave@xxxxxxxxxxxxxxxxxx> Acked-by: Mel Gorman <mgorman@xxxxxxx> --- linux-2.6.git-dave/mm/page_alloc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff -puN mm/page_alloc.c~leak-fix-20121120-2 mm/page_alloc.c --- linux-2.6.git/mm/page_alloc.c~leak-fix-20121120-2 2012-11-21 14:14:52.053714749 -0500 +++ linux-2.6.git-dave/mm/page_alloc.c 2012-11-21 14:14:52.069714883 -0500 @@ -1405,7 +1405,7 @@ int capture_free_page(struct page *page, mt = get_pageblock_migratetype(page); if (unlikely(mt != MIGRATE_ISOLATE)) - __mod_zone_freepage_state(zone, -(1UL << order), mt); + __mod_zone_freepage_state(zone, -(1UL << alloc_order), mt); if (alloc_order != order) expand(zone, page, alloc_order, order, _ -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>